The haptic device is used for inputting the user's motion into computer by the contact with the user's body, and outputting the necessary force or feeling to the user.
Unlike keyboard, mouse, joystick, monitor or printer, which are employing one way interface, the haptic device according to the present invention provides with two way interface which plays a role as a input device for inputting the user's motion into computer as well as the output device for transferring the adequate force or feelings onto the user's body following the commands from the computer. The two-way interface enables the user's direct input and output, aside from facilitating the interaction with the virtual environment of the computer and the tele-operation of the robot that is connected to computer. The two-way interface is emerging as a new paradigm for replacing the existing peripheral devices that are equipped with one-way interface.
FIG. 1 illustrates the general structure of the haptic device according to present invention.
As illustrated in FIG. 1, the user can directly input the user's motion into PC 40 by contacting his/her body with haptic system 1 and manipulating it. The mechanism unit 50 is equipped with the sensor and the actuator (not illustrated in the FIG. 1), which are common to general robots, and the “end effecter” of robots corresponds to the handle 3 with which the user contacts and manipulates. The control unit 30 of the haptic device 1 plays a role in transferring the calculated results of the information detected from the sensor, which is attached to the mechanism unit 50, as well as controlling the actuators attached to the mechanism unit 50 by receiving the commands from the PC 40 and performing mechanical calculations. The control unit 30 can be attached as a form of module or be incorporated to PC 40.
The haptic device, comprising mechanism unit 50, control unit 30 and PC 40 as mentioned above, can be applied to a various technical fields: enabling the direct input with respect to the virtual environment which is prevailing recently, and increasing the sense for the real according to the results generated from the PC 40. In case of complex virtual environments, visual or other kinds of virtual environment can be independently built up with the help of virtual reality system that is equipped with PC for the exclusive-use-only and other components, whilst simple virtual environment can be directly executed in PC 40. The haptic device 1 is connected to the virtual reality system as a subsystem by way of wire/wireless communication. One of other examples of the application of the haptic device is remote operation of the patients or the remote control of robots. In this case, the slave system 200, comprising PC 240 which communicates with remote operation tools and remote robot 210 while setting the haptic device as the master and controls them, can be manipulated in the distance according to the user's will.
While the general robots are designed to have low back drivability lest the disturbances should shake the “end effecter” of robots, the haptic device has to be designed to have the least resistance so that the user can easily manipulate the contacting part of the haptic device. As a result, the haptic device entails more meticulous design specification and higher degree of controlling skill relative to those of the common robots.
The initial haptic devices used series mechanism. The series mechanism has the strong point of spacious workspace and easy analysis. But the series mechanism also has many weak points, e.g. lower precision because of the accumulation of errors at the articulations, and the smaller capacity because of the weak rigidity. In particular, the inertia of the sensors and the actuators that are attached to the respective articulations, inhibit the motion of the mechanism and diminish the back drivability and the efficiency of energy consumption. In the haptic devices with less than 3 degree-of-freedom, series mechanism is frequently employed as above said defects are relatively slim. But in the haptic devices with more than 3 degree-of-freedom, the series mechanism is not preferred because of the increasing number of actuators and the accumulating errors.
The parallel mechanism has a weak point of difficult analysis and narrow work space, but has the strong points in that it endures large amount of loads because of it's structural rigidity and produces high precision because of the destructive interference of the errors. Above all the merits, the parallel mechanism can mount all the actuators on the base, which eliminates the inertia of the actuators from the motion of the mechanism and enhances the back drivability of the mechanism. Accordingly, parallel mechanism is preferred in the development of haptic device with more than 3 degree-of-freedom.
The haptic device can be classified as haptic simulator, haptic arm master, haptic joystick (haptic hand controller), haptic hand master, haptic tactile device according to the contacting part of the user's body.
Haptic simulator is a device for transferring the sense of motions to the entire body of the user while the user is mounted on the device. Haptic arm master is a device for inputting the motion of arms and reproducing the force while the device is mounted on the user's arm. Haptic joystick is a device for inputting the location of hand and reproducing the force, while hand is holding the handle of the device. Haptic hand master is a device for inputting the motion of the fingers and reproducing the sense of shape and volume, while the user is wearing a glove-shaped device. Haptic tactile device is a device for reproducing the touching sense of vibration, temperature or quality of the surface, while contacting the user's skin. Especially, among the haptic devices, the haptic joystick, which inputs the location of hand and reproduces the force while the hand is holding the handle of the device, has superior usability and various fields of application.
In a kinematics and a robotics, the 6 degree-of-freedom is comprised of three translational degree-of-freedom to the direction of x-axis, y-axis and z-axis, and three rotational degree-of-freedom about the x-axis, y-axis and z-axis. In designing the haptic joystick, the pointing device for realizing the three translational degree-of-freedom takes the first place.
In FIG. 2, is illustrated the prior art of 3 degree-of-freedom haptic joystick.
As illustrated in FIG. 2, the prior art of 3 degree-of-freedom haptic joystick realized the translational 3 degree-of-freedom by employing the series mechanism. The user can input translational degree-of-freedom by manipulating the handle 1′ of the haptic joystick with his/her hand, and also the user can perceive the force through the handle 1′ of the haptic device.
However, such device is limited to the motions of translational 3 degree-of-freedom, only.
In FIG. 3, is illustrated the prior art of 6 degree-of-freedom haptic device.
As illustrated in FIG. 3, the prior art of 6 degree-of-freedom haptic joy stick 1″ is realized by combining the rotative mechanism 2, which is capable of rotational motion of 3 degree-of-freedom, to the handle portion of the prior art of translational 3 degree-of-freedom haptic joystick, thus as a whole realizing 6 degree-of-freedom. Famous examples of the prior art of 6 degree-of-freedom haptic devices are the “phantom” and “haptic master” which was developed in Tsukuba University. The “phantom” is a haptic device that realizes 6 degree-of-freedom: the translational 3 degree-of-freedom is achieved by 4-link mechanism, and the additional rotational 3 degree-of-freedom is achieved by attaching rotary mechanism, which is capable of rotation about the x-axis, y-axis and z-axis, to the one end part of the 4-link mechanism.
The “haptic master” of the Tsukuba university has the structure of the upper mechanism attached to the lower mechanism in series, wherein the upper mechanism realizes the rotational 3 degree-of-freedom by using “gimbals mechanism” comprised of 5-link, and the lower mechanism realizes the translational 3 degree-of-freedom using “Maryland parallel mechanism”.
However, the above-mentioned mechanisms are comprised of mechanisms connected in series where the actuators and the sensors are attached to the articulation part. As a result, the motions of the above mechanisms are affected by the inertia of the actuators and the sensors.
The haptic joystick is applied to the technical fields of virtual reality and remote control. Most applications of the virtual reality have the scenario of navigating through the virtual surroundings and performing interactions with the object at some necessary locations. The remote control is used to manipulate various kinds of slave robots in circumstances where human being can't operate properly, like in an atomic reactor, abysmal submarine and spaceship. One example of the remote control is the translation robot equipped with manipulator, “mobile manipulator”, which is used for industrial or military purposes and remote controlled for the purpose of eliminating dangerous substances.
In case of navigating through the plane in the virtual reality, a haptic device with planar degree-of-freedom is adequate. In interacting with the object, the more degree-of-freedom the haptic device can realize, the higher is the sense of reality.
In case of remote controlling of mobile manipulator, the remote-controlled mobile robot approaches the dangerous object and eliminates it. In this case, the haptic device with the same degree-of-freedom with the mobile robot, planar 3 degree-of-freedom, is recommended for the user to directly manipulate the mobile robot.
The above-mentioned cases imply that the haptic device with 6 degree-of-freedom is not always preferable in the aspects of energy consumption, actuator efficiency and control of the mechanism.
As the result of recent research, the methods of simultaneously realizing 6 degree-of-freedom are under development. The mechanisms according to the above method are prominent in precision and back drivability, and exceed the in-series type mechanism in the aspects of efficiency. The examples are the “5-link parallel haptic master” developed by Long and Collins of California state university, “5-link parallel haptic master” developed by KAIST, “haptic master” developed by Sunglcyunkwan University.
In FIG. 4, is illustrated parallel haptic joystick 1″′, which realizes the 6 degree-of-freedom using parallel mechanism.
As illustrated in FIG. 4, the handle 3 of the parallel haptic joystick is connected to the base 14 by way of several links 11, 12. The actuators for the operation of respective links and the sensors for the detection of the movement of links are mounted on the base, and the handle 3 makes 6 degree-of-freedom motions with the composition of the links' movements.
Although above-mentioned parallel haptic master that is capable of realizing 6 degree-of-freedom motion, is superior in objective performances, it is not the most desired type of haptic device. The above-mentioned parallel haptic master has to realize 6 degree-of-freedom through the composition of all the links' movements. Accordingly, it has to operate all the six actuators to make a force feedback, which is only one degree-of-freedom. The above-mentioned haptic devices are usually used under 3 degree-of-freedom environment, and only in special cases the devices are used under 6 degree-of-freedom environment. Considering such circumstances, to operate six actuators all the time is not a good method for the efficiency of energy consumption and control of the mechanism. Instead of operating the surplus actuators for the movement of unnecessary degree-of-freedom, restricting the motion of the components is the better way for the enhanced sense of reality of the feedback force. Accordingly, it is recommended to confirm the kind of frequently used degree-of-freedom, to arrange the components adequate for the frequently used degree-of-freedom, and then to restrict the other components in mechanical way. In addition to the above sequences, additional degree-of-freedom can be added if necessary.